A while back there was a huge hunt to find the original tapes used to record the lunar landing. It is suspected that the tape was re-used due to NASA's tight budget and they couldn't afford more tape. The tape was very expensive at the time so it was common to just re-use what they could find. The Apollo mission was done, so why would they need to keep the tape around. I'm sure it seemed like a good idea at the time.
That or it's stashed under someone's coffee table and forgotten about.